No / Purpose: The aim of this research was to optimize x-ray image quality to dose ratios in the cardiac catheterization laboratory. This study examined independently the effects of peak x-ray tube voltage (kVp), copper (Cu), and gadolinium (Gd) x-ray beam filtration on the image quality to radiation dose balance for adult patient sizes. Methods: Image sequences of polymethyl methacrylate (PMMA) phantoms representing two adult patient sizes were captured using a modern flat panel detector based x-ray imaging system. Tin and copper test details were used to simulate iodine-based contrast medium and stents/guide wires respectively, which are used in clinical procedures. Noise measurement for a flat field image and test detail contrast were used to calculate the contrast to noise ratio (CNR). Entrance surface dose (ESD) and effective dose measurements were obtained to calculate the figure of merit (FOM), CNR2/dose. This FOM determined the dose efficiency of x-ray spectra investigated. Images were captured with 0.0, 0.1, 0.25, 0.4, and 0.9 mm Cu filtration and with a range of gadolinium oxysulphide (Gd2O2S) filtration. Results: Optimum x-ray spectra were the same for the tin and copper test details. Lower peak tube voltages were generally favored. For the 20 cm phantom, using 2 Lanex Fast Back Gd2O2S screens as x-ray filtration at 65 kVp provided the highest FOM considering ESD and effective dose. Considering ESD, this FOM was only marginally larger than that from using 0.4 mm Cu at 65 kVp. For the 30 cm phantom, using 0.25 mm copper filtration at 80 kVp was most optimal; considering effective dose the FOM was highest with no filtration at 65 kVp. Conclusions: These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful option for optimizing patient dose to image quality in cardiac x-ray imaging. The same optimal x-ray beam spectra were found for both the tin and copper details, suggesting that iodine contrast based imaging and visualization of interventional devices could potentially be optimized for dose using similar x-ray beam spectra.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Este trabalho teve como objetivo avaliar a proteção radiológica em procedimentos fluoroscópicos intervencionistas através de testes de controle de qualidade e levantamento radiométrico, bem como a implementação de um objeto simulador para avaliação da qualidade da imagem e sua otimização, com conseqüente redução da dose no paciente. O objeto simulador, desenvolvido para avaliação de equipamentos de radiologia convencional, mostrou-se eficaz na avaliação da qualidade da imagem em fluoroscopia, bem como na determinação dos níveis de taxa de kerma no ar na entrada da pele de um paciente adulto normal. A avaliação dos parâmetros técnicos dos diversos modos de exposição de um equipamento fluoroscópico digital permitiu estabelecer os indicadores de dose para otimização das imagens em procedimentos intervencionistas. Esta otimização possibilita reduzir a dose no paciente mantendo a qualidade da imagem e, conseqüentemente, sem perda de informação diagnóstica. / This work had as main objective to evaluate the radiological protection in the interventional procedures radiology through quality control and evaluations radiometric, as well as the implementation of a phantom for evaluation of the image quality and the consequent reduction of dose in the patient. The developed simulator object for equipment evaluation of conventional radiology had been revealed efficient in the evaluation of the quality of the fluoroscopic image, as well as in the determination of the entrance surface air kerma rate of the normal adult patient skin. The evaluation of the parameters technician in the diverse ways of exposition of digital fluoroscopy equipment allowed establishing the pointers of improve dose for improve the quality of the images in interventionist procedures. This makes possible to reduce the dose in the patient keeping the quality of the image and, without loss of diagnostic information.

No description available.

Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: Detector design and characterization; modulation transfer function; digital fluoroscopy. Includes bibliographical references (p. 150-160).

Accurate, practical, and affordable pose tracking on manually operated C-arm fluoroscopes is a major technical challenge. Conventional tracking methods, such as optical cameras and radiographic fiducials, are hampered by significant shortcomings. Optical cameras are delicate, costly, and have a complex system setup that is easily susceptible to camera obstruction in cluttered operating room. Radiographic fiducials occupy a significant portion of the fluoroscopic imaging space. Using fiducials also requires segmentation that limits clinical use. In this thesis, an alternative form of tracking is proposed to encode the rotational joints of manually operated C-arms using a tilt sensing accelerometer for tracking the C-arm rotational pose. The technique is evaluated by affixing an accelerometer to a full-scale C-arm where a webcam is used as a substitute for X-ray imaging. Ground truth C-arm rotational poses were obtained from the webcam by tracking a checkerboard plate. From these rotational poses, a series of angle and structural correction equations were formulated that can properly relate the accelerometer angle readings to the C-arm rotational pose in real-time and compensate for systematic structural C-arm deformations, such as sagging and bending. Real-time rotational pose tracking of the primary and secondary joint rotations of the C-arm showed an accuracy of 0.5 degrees in the entire range of interest. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-01-28 12:07:32.781

Este trabalho teve como objetivo avaliar a proteção radiológica em procedimentos fluoroscópicos intervencionistas através de testes de controle de qualidade e levantamento radiométrico, bem como a implementação de um objeto simulador para avaliação da qualidade da imagem e sua otimização, com conseqüente redução da dose no paciente. O objeto simulador, desenvolvido para avaliação de equipamentos de radiologia convencional, mostrou-se eficaz na avaliação da qualidade da imagem em fluoroscopia, bem como na determinação dos níveis de taxa de kerma no ar na entrada da pele de um paciente adulto normal. A avaliação dos parâmetros técnicos dos diversos modos de exposição de um equipamento fluoroscópico digital permitiu estabelecer os indicadores de dose para otimização das imagens em procedimentos intervencionistas. Esta otimização possibilita reduzir a dose no paciente mantendo a qualidade da imagem e, conseqüentemente, sem perda de informação diagnóstica. / This work had as main objective to evaluate the radiological protection in the interventional procedures radiology through quality control and evaluations radiometric, as well as the implementation of a phantom for evaluation of the image quality and the consequent reduction of dose in the patient. The developed simulator object for equipment evaluation of conventional radiology had been revealed efficient in the evaluation of the quality of the fluoroscopic image, as well as in the determination of the entrance surface air kerma rate of the normal adult patient skin. The evaluation of the parameters technician in the diverse ways of exposition of digital fluoroscopy equipment allowed establishing the pointers of improve dose for improve the quality of the images in interventionist procedures. This makes possible to reduce the dose in the patient keeping the quality of the image and, without loss of diagnostic information.

No / Purpose: The aim of this research was to explore x-ray beam parameters with intent to optimize pediatric x-ray settings in the cardiac catheterization laboratory. This study examined the effects of peak x-ray tube voltage kVp and of copper Cu x-ray beam filtration independently on the image quality to dose balance for pediatric patient sizes. The impact of antiscatter grid removal on the image quality to dose balance was also investigated. Methods: Image sequences of polymethyl methacrylate phantoms approximating chest sizes typical of pediatric patients were captured using a modern flat-panel receptor based x-ray imaging system. Tin was used to simulate iodine-based contrast medium used in clinical procedures. Measurements of tin detail contrast and flat field image noise provided the contrast to noise ratio. Entrance surface dose ESD and effective dose E measurements were obtained to calculate the figure of merit FOM , CNR2 / dose, which evaluated the dose efficiency of the x-ray parameters investigated. The kVp, tube current mA , and pulse duration were set manually by overriding the system’s automatic dose control mechanisms. Images were captured with 0, 0.1, 0.25, 0.4, and 0.9 mm added Cu filtration, for 50, 55, 60, 65, and 70 kVp with the antiscatter grid in place, and then with it removed. Results: For a given phantom thickness, as the Cu filter thickness was increased, lower kVp was favored. Examining kVp alone, lower values were generally favored, more so for thinner phantoms. Considering ESD, the 8.5 cm phantom had the highest FOM at 50 kVp using 0.4 mm of Cu filtration. The 12 cm phantom had the highest FOM at 55 kVp using 0.9 mm Cu, and the 16 cm phantom had highest FOM at 55 kVp using 0.4 mm Cu. With regard to E, the 8.5 and 12 cm phantoms had the highest FOM at 50 kVp using 0.4 mm of Cu filtration, and the 16 cm phantom had the highest FOM at 50 kVp using 0.25 mm Cu. Antiscatter grid removal improved the FOM for a given set of x-ray conditions. Under aforesaid optimal settings, the 8.5 cm phantom FOM improved by 24% and 33% for ESD and E, respectively. Corresponding improvements were 26% and 24% for the 12 cm phantom and 6% and 15% for the 16 cm phantom. Conclusions: For pediatric patients, using 0.25–0.9 mm Cu filtration in the x-ray beam while maintaining 50–55 kVp, depending on patient size, provided optimal x-ray image quality to dose ratios. These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful strategy for optimizing iodine contrast agent based cardiac x-ray imaging. Removing the antiscatter grid improved the FOM for the 8.5 and 12 cm phantoms, therefore grid removal is recommended for younger children. Improvement for the 16 cm phantom declined into the estimated margin of error for the FOM; the need for grid removal for older children would depend on practical feasibility in the clinical environment. / Philips Healthcare

No description available.

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